As semiconductor device geometries continue to scale down, metal etch processes need to generate more sidewall polymer to achieve a desired metal profile and critical dimension (CD) requirements. The removal of this sidewall polymer has become more difficult. Some of the prior art in-situ resist removal procedures prevent corrosion of the metal layers, but are unable to completely remove the sidewall polymer. Some of the prior art in-situ resist removal procedures prevent corrosion of the metal layers, but also result in a very slow removal of the polymer resulting in a low throughput. Other prior art in-situ resist removal procedures are able to quickly remove the sidewall polymer, but cause unacceptable corrosion of the metal layers.
U.S. Pat. No. 4,736,087, issued on Apr. 5, 1988, entitled "Plasma Stripper With Multiple Contact Point Cathode" discloses a plasma photoresist stripper.
U.S. Pat. No. 5,851,302, issued on Dec. 22, 1998, entitled "Method For Etching Sidewall Polymer" discloses a method for using carbon tetrafluoride CF.sub.4 and water H.sub.2 O as etchant gasses in a LAM 9600 DSQM down stream quartz chamber to remove the entire polymer side wall in a single step. This causes the metal layers to be subject to the CF.sub.4 and H.sub.2 O etchant gasses during this entire single step causing a greater risk of attack or corrosion of the various metal films.
Other art teaches using oxygen O.sub.2, CF.sub.4 and H.sub.2 o as etchant gasses for a period longer than 60 seconds. Such long exposures increases titanium nitride TiN attack or aluminum corrosion. By the end of this period, the semiconductor is heated by a chuck causing even greater TiN attack or aluminum corrosion.
It would be desirable to have a method of in-situ resist removal that completely removes sidewall polymer with a high throughput and a minimal amount of corrosion.